Learning Forum

[AQ]

Hi,

I am working on a positively buoyant offshore platform featuring a large circular deck supported by six buoyant legs. These legs are circumferentially hinged to the deck and taut-moored to the seabed at their bottom ends. My objective is to control the radial motion of each buoyant leg using Magneto-Rheological (MR) dampers. Each leg is connected to an MR damper assembly, with one end of the damper fixed to a central shaft of the platform.

The platform model has been developed in ANSYS AQWA for hydrodynamic analysis.

I would like to know:

1. Is it possible to model MR dampers in ANSYS AQWA for controlling the radial response of the buoyant legs?

2. If not directly, are there any recommended approaches to integrate or couple MR damper behavior with AQWA simulations?

[Mike Pettit]

Hello,

When you create a hinge joint in the hydrodynamic model you can define linear stiffness, damping and friction terms about the rotational axis. Depending on how complex their real-world behaviour is, these parameters may be sufficient to model your dampers.

If the usual joint parameters are not enough, then you can always introduce a user-defined force function (UDF) in your time domain Hydrodynamic Response analysis. This allows you to apply an additional force/moment at the centre of gravity (COG) of each structure, as a function of the position and velocity of each structure's COG at each time step. The UDF can be written as a Python script, and there is an example of this included in the Ansys installation under e.g. C:\Program Files\ANSYS Inc\v251\aqwa\utils\ExternalForceCalculation.

I hope this helps.

Mike

[AQ]

This could be a great help. Let me try.

Thank you, Mike.